history.back button creates problem with session

I am facing problem with the javascript:history.back() function. Following is the scenario.

I have two session open with lets say id S1 and S2 for the same us开发者_JS百科er and single application. Now on session S1 I am on some page say xyz.jsp and on session S2 i am on same page with both the page having back() button which uses the javascript function mentioned above. Also the last action was executed on session S2.(This means after performing action on session2 i have kept both the browser ideal for 15 mins.)

After 15 mins when i came back on session S1 and click on the back button it immediately logs out the user with session S1. It seems that the browser looks for the history page which has the last history of Session 2 and hence it logs out.

I am not sure of actual issue and need your help to illustrate the issue and provide your input.

Thanks, Hanumant